How Hydraulic Fracking Works

Fracking In-depth

Engineers on the drilling platform of the Cuadrilla shale fracking facility on Oct. 7, 2012, in Preston, Lancashire, England. Fracking has been blamed for two minor earthquakes in the surrounding region.

To understand why fracking was developed, imagine a traditional drilling operation. A well works great if we're tapping into a big pool of gas or water underground, allowing us to pump up the resource from the reservoir. But when the resource we're trying to capture is trapped tightly in the pores of shale, how do we release it and bring it to the surface?

It starts off pretty similarly: A deep well is drilled. Chesapeake Energy estimates that the average depth of its wells is 7,700 feet/2,347 meters (roughly six Empire State Buildings stacked end to end [source: Chesapeake Energy]). The Colorado Oil and Gas Association gives the diameter of the hole at 12.25 inches (31 centimeters). When the well reaches the right depth, it takes a right or left turn (referred to as the kick off point) and becomes horizontal. That horizontal section may span 1,000 to 6,000 feet, or 305 to 1,829 meters [source: EPA].

Steel casing fits in the wellbore, aka the hole drilled. The steel is intended to protect groundwater and the surrounding area from any potential leakage during hydraulic fracturing. Down at the horizontal section of the well, the steel is perforated through with a tool that can penetrate the steel and cement of the well to create small holes for water or tiny particles to escape through -- much like your kitchen colander. At that point, a water solution (that we'll explore more later) is pumped in at an extremely high pressure.

When the solution reaches the perforated points, the liquid is too much for the rock to absorb, and the rock cracks. It takes three to 10 days for fracturing to be complete [source: Halliburton]. Additives and sand found in the water mixture hold open these fissures, allowing the gas (or whatever resource) to escape and be brought up to the surface in the water that's pumped back up, and separated. Those resources may flow from the cracks for years or potentially decades [source: Energy in Depth]. The wastewater is stored and treated, pumped into injection wells or recycled; it's also stored in open-air pits or used on roads [source: NRDC].

The equipment that is used in fracking is (predictably) heavy duty. Keep in mind that an estimated 200 tankers are needed to bring 1 million gallons (3.8 million liters) of water to a well, and that deeper shale beds might require 2 to 10 million gallons (7.6 to 37.9 million liters) of water [sources: EarthWorks, ProPublica]. Dozens of "pump trucks" alone are required to shoot the pressurized solution down the wellbore [source: Energy in Depth].

Before we get to some of the issues associated with hydraulic fracturing, let's take a look at some reasons why people are so fracking excited.

Gasland

The 2010 Academy Award-nominated documentary film "Gasland" told the story of residents affected by fracking in their communities. Many recall the (literally) incendiary image of a man lighting his tap water on fire -- supposedly from natural gas contaminating the water supply. Officials in Colorado determined that the leak was a naturally occurring methane reserve that had seeped into the homeowner's well, and not due to fracking. However, there have been fracking-related cases of methane reaching water supplies -- and gas companies who have had to admit their liability and pay hefty fines for their negligence [source: McGraw].